Aluminum gellike absorbent and process for making same



4 Patented June 2, 1 925. a

umrab STATES i-aonmr n wmson, or CHICAGO, rumor-s, ASSIGNOR T was summons ENGINEERING CQRPORATION, or summon MARYLAND.

PATENT O F E- nonunion GELLIKE ABSOBBENT Jinn rnocnss non MAKING same.

No Drawing. Original application filed January 28,

To all whom it may concern Be it known that 1, ROBERT E. WILSON,

a citizen of the United States, residing at Chicago, in the county of Cook and State 6 of Illinois, have invented certain new and useful Improvements in Aluminum Gellike Absorb'ents and Processes for Making Same; and I do hereby declare the following to be a full, clear, and exact description of the 10 invention,such as will enable'others skilled been made both by dialysis of a colloidalsolution of basic aluminum chloride for several days using a semi-permeable membrane and following the procedure commonly used in the preparation of true hydroxide gels, as well as by means of direct precipitation of the hydroxides from solutions of aluminum salts by means of alkalies. While by the former method it was possible to make true aluminum hydroxide gels, the process was so extremely slow and expensive that there was no possibility of its being used as a commercial method of making the gel. On the other hand, the aluminum hydroxides previously made by precipitation, when dried and formed into rough granular material, was found to be soft, resembling soft baked clays and having a ver low absorptive power. .Where any specific direc-.

tions are given for the preparation of precipitated aluminum chloride, complete dehydration is specified. The product, of this invention can be made only when employ- 5 ing the most careful control of the preparation of solutions, (precipitation, and drying.

' It is very hard, ense, and has a vitreous fracture. The best samples hold from 8 to "12per-cent of water after drying several "hours in a vacuum 150 0., while ordinary precipitated aluminum hydroxide is almost completely dehydrated by this treatment. Aluminum hydroxideprepared accordingto' Previous to the method disclosed in this invention a good absorbent, comparing favorably with 1920, Serial No. 35 4,690. Divided and this application filed July 9, 1924. Serial No. 725,037. Y

activated charcoal (with which it may be mixed if desired) against suchgasesas phos gene and chloropicrin. It also has a great capacity for the absorption of water vapor from gases or gaseous mixtures- The material also has, advantages-wherever a dense, Y

firm'structure of aluminum oxide, metallicaluminum, or many aluminum compounds,

are. desired for catalytic and other purposes.

It was found that certainsteps'in the production of this absorbent; constitute im- 'portant variables. in the preparation of an extremely active gel. The aluminum hydroxide is precipitated from a solution of its salts, for instance, aluminum chloride by means of an alkali such as caustic soda and the precipitate filtered and dried. The temper'ature ofthe precipitate, the pressure in the filter press, and the exact method of drying are especially important factors; It was also found that a concentration of solutions-of from. 6 to 10'per cent and a reaction temperature of from 30 to 50 C. gives the bestprecipitate. The solution after pres cipitation should contain an excess of alkali, but not sufficient to appreciatively redissolve the precipitate. Washing byv decant-ation should be very thorough. A fairly high 'pressure should be used in forming the filter cake to squeeze, out all the excess water; The temperature of dryingis important and should not exceed 225 C better results being obtained at temperatures below 200 C. The drying should be slow at the start and is preferably performed in two stages as hereinafter described.

A method of preparation of this absorbout which has been found to give good results is as follows: A 6 per cent solution of aluminum chloride inwater is poured slow "the two so utions being maintained between 30 and -5 0 G.' It is very important that thesolutions be stirred constantly and that the aluminum chloride be poured into. the alkali, not vice versa. The precipitate is washed by'decantation until the wash water 4 shows onl a trace of chlorides. The sludge is fi tered in a filter press at a pres.- sure'of to pounds per square inch, kneaded until uniform, and packed in a cake about one and one-half to two inches deep in screened bottom trays which are put immediately into an oven in a relatively low temperature of (3., with a free ClI'CUhi'. tion of air. When the cake appears perfectly dry, it is removed, ground, and

filter, and thensubject the precipitate to high ressure.

above, certain definite proportions and specific steps are enumerated, it is not intended that this invention be limited to' such details ofprocedure, but it is desired to claim the new gel-like aluminum hydroxide and the process of making the same as set forth in the following claims; for instance, other concentrations of solutions may be used, other alkalies such as ammonium hydroxide may replace the caustic soda in the precipitation and othersalts of aluminum may replace the aluminum chloride. Itis also possible to produce the new absorbent at reacting temperatures varyin somewhat from those specified in the a ve examples.

Alt ough in thespecific examples given WliatI claim and desire to secure by Letters Patent is 1. A hard, rough, partially hydrated, gelgel-like alumidetermined by igniting to a low red heat.

5. An absorbent comprising a' gel-like aluminum hydroxide mixed with absorbent charcoal. I

6. In a process of producing gel-like absorbents, washing by decantation an aluminum hydroxide absorbent after precipitation, and then drying same at about 110 (3., and then at about 15Q? C. I

7 In a process of producing a gel-like ab-- sorbent, washing by'decantation an aluminum hydroxide absorbent after precipitation, kneading and then drying same first" at about 110 (1., in air, :and then about C. in a vacuum. Y

8. In a process .of producing gel-like absorbent, washing -by decantation an aluminum hydroxide absorbent after precipitation, kneading and then drying same at relatively.

low temperature, and finally at a relatively higher temperature.

In testimon'y whereof I afiix my signature. v

. ROBERT E. WILSON. 

